> >What if the language in question already has an [r] -- will the pre-existence
> >of such a sound tend to hinder this change?
>
> Not at all. Latin did this sort of change (example: os, osis "mouth"
> became os, oris) whereas the 'r' already existed (like in orator, oratoris
> which has always been like that even when we had os, osis).
>
> How about de-voicing of [r]s?
> >One particular hypothetical dialect of Aroven does that, giving a sort of
> >dry fluttering sound in place of the [r] which sounds a lot like an [x];
> >/r/ is probably the most "unstable" letter in the language...
>
> I think de-voicing of [r] is likely to happen near to a voiceless
> consonnant. Between vowels, it seems very unlikely to me.

Right -- when it's between two vowels it turnes into a flap instead :)
For example, in this dialect 'Arove"n' is pronounced, more less, [Ad' o ven],
initial r's are pronounced [hr] and r's which precede stops (any stops, not
only voiceless ones) and nasals are devoiced (e.g. karn [k&rn] -- is there
an ASCII IPA symbol for a devoiced [r]?), especially if that stop or nasal is
followed by another vowel (e.g. karna -- sounds like [k&' hna] with a fluttered
[h]).
Josh